One of the most challenging groups of kids for the city to teach over the years has been English Language Learners — especially new immigrants who enter the system for the first time in high school.

Yet one of the best performing schools in recent years — the Gregorio Luperon HS for Science and Mathematics in Washington Heights headed by Principal Juan Villar — has a student body composed of 90 percent non-native English speakers.

Despite the challenges, the high school’s graduation rate has soared by more than 22 percentage points in recent years — from 56.4 percent in 2005 to an above-average 79 percent in 2008.

“All the teachers are really great,” said Michael Fermin, a 17-year-old junior who moved to the city from the Dominican Republic two years ago. “Before, I couldn’t speak English. Now I can speak — and I want to get better.”

Part of the school’s success stems from the fact that it sets the bar high. It offers Advanced Placement classes in numerous subjects and college-credit-bearing courses through City College.